Foot control for dental engines



March 9, 1954 H. E. CRAWFORD FOOT CONTROL FOR DENTAL ENGINES 4Sheets-Sheet 1 Filed July 30, 1949 VENTOR W ATTK m Z BY g Marcfi 7E5 1H. E. CRAWFORD FOOT CONTROL FOR DENTAL ENGINES 4 Sheets-Sheet 2 FiledJuly 30. 1949 March 9, 1954 CRAWFORD 2,671,258

FOOT CONTROL FOR DENTAL ENGINES Filed July 30, 1949 4 Sheets-Sheet 5 INVEN TOR,

March 9, 1954 H. E. CRAWFORD FOOT CONTROL FOR DENTAL ENGINES Filed July50. 1949 4 Sheets-Sheet 4 II E-11- TIE-1Z- Patented Mar. 9, 1954 UN ITEDSTATES PATENT OFFICE FOOT "CONTROL FOR. DENTAL ENGINES Howard-E.Crawford, Toledo, Ohio ApplicationiulyBll, 1949, SerialNo. 107,740

rl l-nqlaims. (Cl. 32-23) This invention relates to a foot control fordental engines.

An object of this invention is to provideafoot operated switch systemwhich permits adentist to stand with both feet firmly :on the supportingplane, retaining a comfortable posture while working, and retain fullcontrol of the dental engine which entersinto th-e performance of amajor portion of dental operations.

Another object ofthis invention is to provide a foot controlled switchfor the circuit of a dental.- engine, which swltchmay be manipulated bya slight turn of the foot. The operator, through foot manipulation, hasfull control of the dental engine, imparting at will every functionnormally ifurnishing tool control by the engine.

vAnother object of this invention.- is to provide a switch mechanism forthe full control of a dental engine which permits the operator to standthereon and intentionally control the same, yet may beinadver-tentlystepped upon without imparting-operation-or damage to theengine 01' to the "system.

Another object of this invention is "to provide a switchmechanismwhich-maybe operated to select aspeed for the dental engine, repeatedlyoperated :to cause the engine to runat the same speed or manipulated tochange the speed.

Another object of this invention is to provide a switch mechanism'forthe circuit of adental engine which'permits anoperator to-select'a'speed of operation, determine the direction of rotation andautomatically brake the rotation to stop following each selected andcontrolled function.

And another object of thisinvention is -to providea switch mechanismwhich is readily accessible-to the operator when needed but will notintroduce a stumbling hazard to himself -or to a patient as they move.normally :aboutthe-dental chair.

Heretofore inthe general practice of dentistry, the dentist has been'forcedto work while maintaining an unnatural Orrather a strainedposture, that is supporting the major "portion of his weight on one footin ordertoleave the-other foot free to operate a 'switchmechanism-whichin turn controlled" his engine. By-thisinvention, one 01 more switchmechanisms of 'the type-disclosed may "be inserted into thefioor aboutthe dental chair, or maybe' built'into 'a mat horizontally placedadjacent the chair, whereby the dentist :can distribute his weight 'toboth feet and operate ;the switch with either foot, retain- .ingifull:control :of "the-engine "and" increasing his 2 freedom of operation.Thus fatigue is lessened and occupational diseases, heretoforeattributed to the strained stance, are materially'decreased.

A plurality of the switch mechanisms may be disposed aboutachair in sucha manner that the dentist may operate upon a patient from the mostconvenientposition, while retaining-full control oi-his enginedriven-tools, with no interference from the switches nor theirconnections.

Other objects and advantages to be derived from this invention resultingfrom the'arrangement, operation and function of the related elements inthe structure, tovarious details of construction, to combinations ofparts and to economies of manufacture, will be apparent to those skilledin the art upon consideration of the-followingdescription and appendedclaims, reference being had to the accompanying drawings forming a partof this'specification wherein like reference characters designatecorresponding parts in the several views.

Referringto the drawings:

Fig. 1 is a-perspective view of a'dental chair showing a typicalinstallation and embodying features of the invention herein;

Fig. 2 is a view on the line II-II, Fig. 1;

Fig. 3 is aside elevation of a link-in the articulated mounting for adentists hand-piece including a hook upon which the hand-piece maybeplaced when notin use and including a switch housing for a hook operatedswitch;

Fig. 4'is an enlarged view ofthe switchportion of the hand-piece hangerof Fig. 3, the cover being removed exposing details of the switchoperating mechanism;

Fig. 5 is a plan view of a foot controlled switch mechanism of theinvention herein, 'parts'being broken away;

Fig. 6 is a view similarto Fig. 5, with the-control pedal broken away,and the switch-parts-in a forward speed position;

Fig. 7-is a viewon the line VII-VILFig. '5;

"Fig. 8 is a view similartoFig. ,6, with the switch parts in reverseposition;

*Fig. 9 is a'detail'similarto Fig. '7, interlocked for indexing;

-Fig.'10 isa wiring diagram of a dental engine circuit'incorporating aplurality of controlswitch mechanisms;

-Fig. 11 isa plan'view .of a modified jform of the switch mechanism; and

Fig. 12 is a wiring diagramotadental engine circuit incorporating .asingle control switch with the ,parts mechanism of; the typeillustratedin Figgll.

Dental chair"20 is shown with the usual adjacent accessory pedestal 22,with its column 24 mounting the dental engine 2% from which artic ulatedpower transmission support 28 extends to carry hand-piece 30. Thishand-piece embodies a chuck for the mounting of the various toolsemployed in the art of dentistry, the proper operation thereof requiringa critically controlled speed, direction of rotation, and brake ofrotation, all instantaneously responsive to the operator.

When the hand-piece is not in use, it is hung upon hook 32 pivotallymounted. and extending from housing 34, which housing, for convenience,forms a portion of the articulated structure 28 extending from theengine 26to the hand-piece, I

the utility of this construction being more fully discussed hereafter inconnection with the electric circuit for the engine 26.

The demands of present dentistry call for a dental engine, referred toin the profession as such, which in reality is an electric motor havinga plurality of speeds in both directions of rotation, and in operationhaving an instantaneous brake to stop the rotation upon eachdeenergization of the armature circuit in the motor.

For purposes of illustration, the motor 28 herein is shown as havingfour speeds, forward or reverse, determined by suitable shunts 36, 30,and 42 placed in the circuit thereto. The

value and number of the shunts are pre-selected and for convenience maybe disposed in a housing 44 accessibly mounted within the pedestal 22.The shunt 36 is a permanent protective shunt and fixes the maximum speedat which the motor can run.

The wiring necessary for satisfactory operation of the circuit is placedin conduits substantially concealed Within the equipment so that thereis no interference with the operators technique.

The lines which extend to the foot controlled switch mechanism may beplaced Within a conduit 46, extending from the pedestal 22 into andthrough floor mat 48, while a flexible conduit 4i extends from thepedestal along the support 28 into the housing 34.

a The floor mat is preferably a resilient pad, a typical constructionincluding a sponge rubber base 50, topped with a layer of linoleum or alike wear surface 52. The mat has a feathered perimeter 54 bounding apredetermined area about the chair 20 encompassing the floor space usedby the dentist while operating upon a patient in the chair. Thisprovides a comfortable continuously horizontal level footing and allowsfor a decorative floor pattern.

One or more of the foot controlled switch mechanisms of the inventionherein are conveniently positioned in the pad about the chair.

A preferred form of the switch mechanism includes a sheet metalcup-shaped member 56 embedded in the pad and to which the conduit 46extends with the lines therefrom distributed about the chamber 58 withinthis housing to properly interconnect the various elements disposedtherein.

This member 58 may have its bottom 60 resting on the floor 62 whichsupports the mat thereby providing a substantial foundation. The rim 64of this cup mounts a peripheral ring 66 having its upper face 68substantially flush with the wear surface of the mat and having aninwardly and downwardly dished portion TI] terminating in a trough 12about central opening 14 into the chamber 58. This ring 66 may overlapand ail) squeeze the edge of the mat about this switch housing toprovide a trim appearance and a continuous face from the mat to theoperating element is of the mechanism. The edge of the mat about the cupmay be clamped between the ring 66 and cup by means of bolts I8.

The operating element I6 includes a resilient dome-shaped shell set in arevoluble frame 82 havinghub 84 mountedon roller bearing 85 in turnmounted on staff oraxle 88 upwardly extending centrally in the chamber58 from the bottom 60 of the member 56. The frame 82 is provided with aperipheral overhang 98 above the trough I2 cooperating therewith to keepthe chamber 58 free from foreign matter entering thereinto by way of theopening 14.

Coaxially mounted about the hub 84 and spaced therefrom'is a bearingring 92 serving as an axle for flanged ring 94 to rotate thereon. Thisring 94 has a cam 96 fixed therewith together with a ratchet or toothedwheel 98 superimposed thereon. Rotation of the member 98 thereforerotates the cam 96. This cam is provided with a number of detents I00 inits periphery. The number of detents depends upon the number of switchesto be operated thereby. Herein there are involved three cam operatedswitches I02, I 04 and I055. The operation demanding only one switch tobe closed at a time, the number of detents is seven. This positions thedetents so that only one of the switches I02, I04 or I06 is closed at agiven time, and rotation of the cam 96 will close such switches insequence, that is switch I02 first, then switch I04, then switch I06,and when any one is closed, the other two are open. Durin the change,all switches in this bank may be momentarily open. Adjustments as to theswitches result in a smooth opening and closing sequence, one flowinginto the other.

A step by ste rotation of the cam 96, as driven by the member 98,operates this speed-control bank of switches to determine the cutting inand out of the shunts 88, 40 and 42.

Rotation of the cam 96 is controlled by foot operation against the dome80. The dentist desiring to operate the engine, assumes a natural stancewith both feet on an even level upon the platform 48, shifts either footonto the dome 80 and lifts the hand-piece 30 from the hook 32. Thesequence of these operations is immaterial. A resultant automaticlifting of the hook 32 causes switch I08, within the housing 34, toclose. This switch I08 is in power line IIO feeding the circuit, whilethe other power line II2 into the circuit includes the motor fieldwinding.

Pressure against the pad or dome 80 depresses the same, or rather thecentral portion thereof, against the resistance of leaf spring II6,having one end thereof fixed to the frame 82 and the other or free endabuttin against the underside of the dome. The dome itself is aself-supporting elastic shell with a corrugated or ribbed exposedsurface to be engaged by the undersurface of a foot and the spring H6 inaddition to serving as an auxiliary support and reset aid also operatesadditional mechanism. A flexible extension H8 is attached to the freeend of the spring with the extensions remote or outer end terminating ina flanged offset I20 extending downwardly through slot I22 into thechamber 58. A depression of the dome against the resistance of thespring imparts a radial and downward thrust to the flange I20. Thedownward movement is interrupted by the flange abutting flexible wingI24 of pawl element I26 pivotally mounted on pin I28 anchored in theframe a: for mcvemenI; therewith and normally held ii). non-ratchetengaging position by spring I 29 mounted about'the pm 128.

The first depression and rotation of the dome does not afiect the "motorcircuit speed switch bank. Depression of the come onl does not affectthe motor "circuit in any manner 'b'utmerely shifts the flange I20 toabut the wing I24 with the extension II8 placed under tension.Thereforeit is obvious, walking over the mat and inadve'rtently steppingon the dome does not operate nor injure the mechanisms.

The dentist rotates the dome in a clockwise direction if he wishes torun the engine forward and he rotates the dome in a counterclockwisedirection if he desires the engine to run in "reverse.

A rotation of the frame clockwise simultaneously accomplishes severalcontrols. The Wing I24 slides along pin I30 mounted on thecup bottom 60,causing the wing to be swung inwardly .and from under the flange I andthe extension H8 springs the flange into interlocking engagement withthe wing to hold it in its inward position until pressure on the dome isrelieved.

The pawl element 1-26 does not engage the member 98 until swung intoengaging position by pin I during the first clockwise rotation of theframe and the =co-relation of pin I30 and pawl element I26 and wing I24is such that pawl I26 is not brought into engagement with the toothedmember 98 until after it has cleared the indexing or driving tooth thatit would normally have engaged if it had been held in ratchet engagingposition by the flanged offset I20 at the start of the rotationmovement. Successive swivels, if in the meantime, the wing I24 has notbeen freedirom the flange I20 by a lifting of the operators foot, willcause the pawl I26 to drive the ratchet step by step thereby changingthe operating relationshipof the speed-control switches. The firstdepression and turn of the foot does not change the speed of the motorbut causes the motor to run at the same speed at which it was operatingin its previous run, so a dentist following each cut out of the engine'by ting each step and a spring finger I34 positioned toengage themember I26 and prevent indexing of more than one tooth when the pedal ismoved from neutral or zero in a clockwise movement.

The frame 82 includes a peripheral skirt I36 surrounding the speedcontrol switches and in coaxial relationship with the axle88,'whichskirt is provided with cam regions I30, I40, I 42 and I for operating agroup of switches I46, I48, I50 and I52, in turn controllingfunctions'of the motor 26 other than speed variation. For exampleswitches M6 and I48 may be operated to reversethe motor, switch I50 tocut inthe'armature brake shunt and coupler switch I52 to connect thecommon speedcontrol shunts in series with any of the switch mechanismsdisposed about the platform or rather interconnect the 'particularswitch in operation with'the shunts.

with each clockwise shirt or the frame, the switch -1'52 closes toconnect the spe'edfswitch bank of the pedal being operated into -thecircuit, the brake switch I 50 opensthe 'shunt 'across the armature,whilethe reverse "switches I IISan'd I38 retain their polarity.

In -a counter-clockwise shift, the switches I52 and I50 operate in thesame manner but the reverse switches change their polarity. Thesemovements are all determined by the positioning andexte'nt of thecamregions andth'eir coac'tin'g switches.

Means are provided to limit the extent of the clockwise andcounter-clockwise shift to predetermined arcs. To this end, -arm I54radially extending from the frame 82 terminates in a bearingconstruction I56 shiftablealong arcuate "slide bar I58. The mo'veme'ntclockwise is against the resistance of spring I60 compressible between abearing portion I56 and the terminal mount I-52 for the bar I58. "Thecounter-clockwise shift is against the resistance of spring I64compressible-between the bearingportion I56 andterminal mount I66 forthe bar I58. Upon release'of the foot from the dome '80, the springsreturn'the mechanism to neutral.

A resilient shock absorber I 68 is 'providedadjacent the forward stop iI10. This-resilientmean's eases the shock as it builds up resistanceinthe approach toward the limit I 10 and'in repeated operation of thepedal dur'ing indexing lessens the possibility of the operators footcreeping across the dome even though thedeme' presents a non-skidoperating surface.

A resilient take-up may beemploy'ed for the reverse but in that reversemovement is'so seidom used consecutively, a fi-xed 'stop I12 "appearssuificient. I

For purposes of stability and eas'e of'inovement, a thrust bearingincluding a roller track I14 is provided as a support 'fo'rthe frame 82,the flower race or track supporting the bearing being mounted on thebottom '60 of the cup-shaped housing and positione'd to support theframe just insideth'e skirt I36. Th'e-race I14 is horizontally piercedbelow its top surface by clearways I1 5 for wiring to extend'therethrough "to the speed switches. The skirt I36 hascorresponding-clearways I".

Asshown in Fig. 1 and inF'ig. l0, a plurality of duplicate switchmechanisms may be used connected into acommon circuit.

The mechanism is readily installed into existing apparatus, thehand-piecehook carrying portion of the articulated transmissioni'sreplaced by a link H6 mounting the housing :34. The housing -maybedispose'd in the pedestal-221i desired, or in some remote place outofthe way, with proper conduits therefrom to the vhousing 3'4 and'to themat.

With the lifting of the operators foot, switch I50 is-efiective toplace'a'shunt acrossthe motor armature circuit thus servin as a brake tobring the motor 'to "an instantaneous 'stop preventing any overrun of.the tool after the foot is lifted. This provides the critical controlnecessary for dentistry.

The mechanism is readily adaptable to variations in installation and inconstruction and as many units as desired may be placed-adjacent achair. For example, even asingle unit may be employed with theelimination of switch I52. This would be advantageous inpor'table dentalcenters.

The camrsfi may be replaced -bymfwhee1- I18 carrying a series ofconductor plates I80 insulated from each other, the lines from theresistances 38, 40 and 42 and from the power line H2 are provided withspring finger terminals I82 which may all engage a plate I80 and as thewheel I18 rotates step-by-step, the fingers will spring from one plateto the succeeding plate in sequence to control the speed of the motor.

It is to be understood that the above detailed description of thepresent invention is intended to disclose an embodiment thereof to thoseskilled in the art, but that the invention is not to be construed aslimited in its application to the details of construction andarrangements of parts illustrated in the accompanying drawings, sincethe invention is capable of bein practiced and carried out in variousways without departing from the spirit of the invention. The languageused in the specification relating to the operation and function of theelements of the invention is employed for purposes of description andnot of limitation, and it is not intended to limit the scope of thefollowing claims beyond the requirements of the prior art.

What is claimed and desired to be secured by United States LettersPatent is:

1. In a foot control means for selectively operating a bank of switches,a platform of at least sufiicient lateral extent to support both feet ofan operator on even level, a mechanism for selectively operating theswitches inset in said platform, a control member for said mechanismcomprising a resilient shell providing an axially depressible androtatable element having at least a portion extending slightly above thesurface of said platform to be engaged by an operators foot, and meansfor detachably connecting and operating said control member to saidmechanism responding to the axial depression of said resilient shell toinitiate a mechanical operation in connection therewith which is furtheroperable by the rotation thereof.

2. In a foot control for an electric motor, a resilient platform of atleast suflicient lateral extent to support both feet of an operator oneven level, a cup-shaped member inset into said platform and having aperipheral flange outwardly extending to engage the surface of saidplatform around said member, means locking said member in the platformand compressing the flange thereinto so that the upper surface of saidflange provides substantially a continuation of the supporting area ofthe platform, a bank of switches in said cup-shaped member, mechanismfor operating said switches, a control element for said mechanismcomprising a dome-shaped compressible member having its perimeteradjacent the interior of said cup-shaped member and arched outwardlytherefrom to provide a foot-engaging area rising slightly above andwithin the flange, and means operable by compression and rotation ofsaid control element to interlock with and operate said mechanism.

3. In an electric switch mechanism, a housing providing a support, aframe rotatable on said support, spring means operable to position saidframe in a neutral position, a control for said frame comprising anelement mounted thereby and providing a face to be engaged by anoperator to rotate said frame against the resistance of said spring anddepress said element toward the frame, additional spring means operableto urge said element longitudinally away from said frame, a membermounted by said frame and radially shiftable by the movement of saidelement, a

switch operating device, means carried by and operable to interlock saidradially shifted member to said switch operating device upon rotation ofthe control element, and an electric switch operable by said switchoperating device.

4. Mechanism for operating an electric switch comprising a housing, asupport fixed therein, a. frame rotatable on said support, meanscoacting between said frame and said support adapted to urge said frameto a neutral position, a control for said frame comprising an elementmounted thereby and providing a face to the exterior of the housing tobe engaged by an operator to depress said element toward the frame andto rotate said frame, means limiting the rotation of said frame to anare from the neutral position, spring means urging said element from theframe, a member mounted by said frame and shiftable radially outwardupon shifting of the element toward the frame and withdrawn throughoperation of the spring means upon release of said element, a switchoperating mechanism, a switch to be operated thereby, and meansextending from said radially shiftable member for interlocking saidmechanism for operation with said outwardly shifted member upon rotationof said control.

5. Electric switch mechanism embodying a cupshaped housing, a framerotatable in said housing, a support for said frame, a dome-shapedelement having its perimeter mounted on said frame with its centralportion outwardly arched toward the open side of said cup-shaped housingand fiexible toward and from the frame, an electric switch in saidhousing, a rotatable cam for operating said switch, a ratchet and pawlmechanism for imparting a step-by-step rotation of said cam, and meansextending between said dome-shaped element and said pawl operable byflexing said element toward the frame and rotating the same, to throwsaid pawl into engagement with the ratchet, with a subsequent rotationof said cam upon a repeat rotation of said flexed element.

6. In an electric switch mechanism, a rotatable cam, a bank of switchesabout said cam, said cam adaptable to selectively operate the switches,mechanism for imparting a step-by-step rotation to the cam embodying aratchet fixed with the cam, a pawl for coacting with said ratchet, arotary frame mounting said pawl, a support for said frame, meanscoacting between said pawl and support for urging said pawl towardratchet engagement upon rotation of said frame, a pad on said frame,means movable upon operation of said pad to engage said pawl andmaintain said pawl in ratchet operating position.

7. In a switch mechanism, a rotatable frame, a support for said frame, acam carried by said frame, an electric switch, said cam adaptable tooperate said switch upon rotation of said frame, a pad mounted by saidframe, said pad adapted to rotate said frame and to be depressedtheretoward, a rotary cam, mechanism operable to rotate said camstep-by-step, a switch operable by said rotary cam, and means operableby said pad to interlock said rotary cam operating mechanism with saidframe whereby rotation of said frame may operate both cams andconsequently the two switches.

8. In a switch mechanism, two banks of electric switches, a pad forcontrolling said mechanism in turn selectively operating the two banksof switches, said pad having longitudinal and rotary movements, arotatable frame for mounting said pad, a support for said frame, a camcarried by said frame for operating the first bank of said switches,means operating the second bank of switches in a predetermined sequence,and means operable by longitudinal and rotary movement of said pad toselectively interlock said frame with the second switch bank operatingmeans whereby both banks of switches may be controlled by rotation ofsaid frame.

9. A switch mechanism embodying a housing, two banks of electricswitches in said housing disposed in coaxial relationship about a commoncenter, a frame rotatable about the center, a support for said frame,said frame having a skirt providing cam regions operating the outer bankof switches upon rotation of said frame, a, cam mounted for rotationabout the center adapted to operate the inner bank of said switches, aratchet and pawl drive for said latter cam, a pad carried by said frame,and an element shiftable as to said frame by depression of said pad,

m mi

an electric switch, a cam for operating said switch, a ratchet and pawlmechanism for driving said cam, and interlocking means for said springshifted element and pawl operable by rotation of the frame by saidcompressible member.

11. In combination, a dental engine, a circuit for controlling saidengine, an articulated support from said engine, and a tool carried bysaid support; a foot operated switch in said circuit for controllingsaid circuit to impart selected functions to said engine, and a switchin said circuit mounted on said articulated support embodying anactuator to receive said tool and open said switch, said latter switchrendering said circuit inoperative when supporting said tool.

HOWARD E. CRAWFORD.

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